Composition containing a mixture of hexa-alkyl disilazane and propylene glycol alkyl ether and/or propylene glycol alkyl ether acetate

ABSTRACT

The invention provides a composition which comprises from about 3 to about 50% by weight of a hexa-alkyl disilazane and a solvent composition which comprises one or more compounds selected from the group consisting of a propylene glycol alkyl ether and a propylene glycol alkyl ether acetate.

This is a divisional of co-pending application Ser. No. 06/791,876 filedon Oct. 28, 1985, U.S. Pat. No. 4,692,398.

BACKGROUND OF THE INVENTION

The present invention relates generally to the field of radiationsensitive positive and negative photoresist compositions andparticularly to compositions containing novolak resins together withnaphthoquinone diazide sensitizing agents.

It is well known in the art to produce positive photoresist formulationssuch as those described in U.S. Pat. Nos. 3,666,473, 4,115,128 and4,173,470. These include alkali-soluble phenol-formaldehyde novolakresins together with light-sensitive materials, usually a substitutednaphthoquinone diazide compound. The resins and sensitizers aredissolved in an organic solvent or mixture of solvents and are appliedas a thin film or coating to a substrate suitable for the particularapplication desired.

The novolak resin component of these photoresist formulations is solublein alkaline aqueous solution, but the naphthoquinone sensitizer acts asa dissolution rate inhibitor with respect to the resin. Upon exposure ofselected areas of the coated substrate to actinic radiation, however,the sensitizer undergoes a radiation induced structural transformationand the exposed areas of the coating are rendered more soluble than theunexposed areas.

The relief pattern of photoresist on substrate produced by the methoddescribed above is useful for various applications including, forexample, as an exposure mask or a pattern such as is employed in themanufacture of miniaturized integrated electronic components. In manyindustrial applications, particularly in the manufacture of miniaturizedelectronic components, a photoresist is required to provide a highdegree of resolution for very small line and space widths (on the orderof one micron or less).

The ability of a resist to reproduce very small dimensions, on the orderof a micron or less, is extremely important in the production of largescale integrated circuits on silicon chips and similar components.Circuit density on such a chip can only be increased, assumingphotolithography techniques are utilized, by increasing the resolutioncapabilities of the resist. Although negative photoresists, wherein theexposed areas of resist coating become insoluble and the unexposed areasare dissolved away by the developer, have been extensively used for thispurpose by the semiconductor industry, positive photoresists haveinherently higher resolution and are utilized as replacements for thenegative resists.

This invention relates to a composition for stripping, thinning,cleaning and promoting the adhesion of cured and uncured photoresistcompositions on substrates covered with such resists and to thestripping process using such compositions.

Both mechanical and chemical processes are known for the removal of theaforementioned resinous coatings from a substrate, but these processesleave much to be desired. If the cured coating is mechanically strippedas by scraping, the removal of the material is almost invariableaccompanied by some physical damage. The use of certain chemicalreagents or solvents, formerly employed, is unsatisfactory since theydissolve the cured resins either too slowly or incompletely or both, orthey comprise the electrical reliability by leaving residualcontaminants which are not completely removed by subsequent processing.A solvent or stripping solution which will both quickly and completelyremove the aforementioned cured resins from the substrates withoutdamage or contamination thereof is therefore needed.

Solvent compositions are known which may be used for thinningphotoresist compositions, stripping undesired cured and uncuredphotoresist from wafers, removing undesired edge bead from spunphotoresist wafers and cleaning related photoresist processingequipment. However, such compositions are generally extremely toxic,ecologically undesirable and/or are unpleasantly odorous.

The present invention seeks to solve the aforementioned disadvantages.

A positive working photoresist comprising propylene glycol alkyl etheracetate is described in U.S. patent application Ser. No. 619,468 filedJune 11, 1984, as well as U.S. patent application Ser. No. 791,252,filed on Oct. 25, 1985, and which are incorporated herein by reference.

A positive working photosensitive composition comprising a mono C₁ to C₄alkyl glycol ether of 1,2 propanediol is described in U.S. Pat. No.742,063 filed June 6, 1985 and is incorporated herein by reference.

A positive working photosensitive composition comprising a mixture ofpropylene glycol alkyl ether acetate and propylene glycol alkyl ether isdescribed in U.S. patent application Ser. No. 791,880, filed on Oct. 25,1985 and is incorporated herein by reference.

Photoresist treating compositions containing only one of propyleneglycol alkyl ether and propylene glycol alkyl ether acetate have adisadvantage. Propylene glycol monomethyl ether acetate (PGMEA) has anoffensive odor to approximately one-half the people who came in contactwith it. These are usually women. Propylene glycol monomethyl ether(PGME) is also offensive to approximately one-half the people who areexposed to it. These are usually men. However, those who find PGMEAoffensive find PGME to have little or no odor. The reverse is also true,those who object to PGME find PGMEA to be pleasant or not objectionable.Mixtures of these solvents i.e. PGME/PGMEA (1:1) are not objectionable,or at least less objectionable to both groups of individuals. Based onthese observations photoresist treating compositions using PGME/PGMEAmixtures form a class of reduced odor compositions.

SUMMARY OF THE INVENTION

The invention provides a composition which comprises from about 3 toabout 50% by weight of a hexa-alkyl disilazane and a solvent compositionwhich comprises one or more compounds selected from the group consistingof a propylene glycol alkyl ether and a propylene glycol alkyl etheracetate.

The invention also provides a method of treating a photographiccomposition which comprises contacting said composition with a mixturewhich comprises from about 3 to about 50% by weight of a hexa-alkyldisilazane and a solvent composition which comprises one or morecompounds selected from the group consisting of a propylene glycol alkylether and a propylene glycol alkyl ether acetate.

Most preferably the acetate is propylene glycol methyl ether acetate.The most preferred ether is propylene glycol methyl ether. Both theether and acetate preferably contain C₁ to C₄ alkyl units.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the production of photoresists, preferably positive workingphotoresists, the skilled artisan provides a photosensitive compositioncontaining a novolak or polyvinyl phenol resin, a quinone diazidephotosensitizer and a solvent composition.

The production of novolak resins, which may be used for preparingphotosensitive compositions, is well known in the art. A procedure fortheir manufacture is described in Chemistry and Application of PhenolicResins, Knop A. and Scheib, W.; Springer Verlag, New York, 1979 inChapter 4 which is incorporated herein by reference. Polyvinyl phenolsare described in U.S. Pat. Nos. 3,869,292 and 4,439,516, which areincorporated herein by reference. Similarly, the use of o-quinonediazides is well known to the skilled artisan as demonstrated by LightSensitive Systems, Kosar, J.; John Wiley & Sons, New York, 1965 inChapter 7.4 which is also incorporated herein by reference. Thesesensitizers are selected from the group of substituted naphthoquinonediazide sensitizers which are conventionally used in the art in positivephotoresist formulations. Such sensitizing compounds are disclosed, forexample, in U.S. Pat. Nos. 2,797,213; 3,106,465; 3,148,983; 3,130,047;3,201,329; 3,785,825; and 3,802,885. Useful photosensitizers includenaphthoquinone(1,2)-diazide-5-sulfonyl chloride, andnaphthoquinone-(1,2)-diazide-4-sulfonyl chloride condensed with phenoliccompounds such as hydroxy benzophenones.

The solid parts of the photoresist composition, that is the resin anddiazide ranges from 15% to about 99% resin and from about 1% to about85% quinone diazide. In manufacturing the resist composition the resinand diazide are mixed with a solvent composition comprising, forexample, xylene, butyl acetate and Cellosolve acetate in amounts fromabout 40% to about 90% by weight of the overall resist composition.

In the preferred embodiment, the hexa-alkyl disilazane is hexa-methyldisilazane. It is preferably present in the present composition in anamount ranging from about 3-50% by weight or more preferably 5-30% byweight.

The solvent composition comprising propylene glycol alkyl ether (PGME)and propylene glycol alkyl ether acetate (PGMEA) is preferably presentin an amount ranging from about 50% to 97% by weight or more preferably70% to 95%. Other solvents may also be included but these are notpreferred.

In the preferred embodiment the ratio of PGME to PGMEA can vary in abroad range depending on the desires of the user. One suitable range ofsuch ratios is from about 1:10-10:1. A preferred range is from about7:3-3:7, more preferably about 6:4-4:6. In the most preferred embodimentthe PGME and PGMEA are present in approximately a 1:1 ratio.

Additives such as colorants, dyes, anti-striation agents, plasticizers,adhesion promoters, speed enhancers, solvents and such surfactants asnon-ionic surfactants may be added to the solution of resin, sensitizerand solvent composition before the solution is coated onto a substrate.

The prepared resist solution, is applied to a substrate by anyconventional method used in the photoresist art, including dipping,spraying, whirling and spin coating. When spin coating, for example, theresist solution can be adjusted as to the percentage of solids contentin order to provide coating of the desired thickness given the type ofspinning equipment utilized and the amount of time allowed for thespinning process. Suitable substrates include silicon, aluminum orpolymeric resins, silicon dioxide, doped silicon dioxide, siliconnitride, tantalum, copper, polysilicon, ceramics and aluminum/coppermixtures. When the photoresist is whirl coated on a wafer substratethere is a tendency for a bead of photoresist to accumulate on the waferedge. The composition of this invention effectively causes this bead toflow by spraying the composition onto the revolving edge bead. Thus theresist thickness is substantially uniform across the wafer surface. Thehexa-alkyl disilazane increases the composition solubility.

After the resist composition solution is coated onto the substrate, thesubstrate is temperature treated at approximately 20° to 105° C. Thistemperature treatment is selected in order to reduce and control theconcentration of residual solvents in the photoresist throughevaporation while not causing substantial thermal degradation of thephotosensitizer. In general one desires to minimize the concentration ofsolvents and thus this temperature treatment is conducted until asubstantial amount of the solvents has evaporated and a thin coating ofphotoresist composition, on the order of a micron in thickness, remainson the substrate. This treatment is normally conducted at temperaturesin the range of from about 20° C. to about 105° C.

The exposed resist-coated substrates are usually developed by immersionin an aqueous alkaline developing solution. The solution is preferablyagitated, for example, by nitrogen burst agitation. Suitable developersnon-exclusively include water solutions containing an alkali hydroxide,ammonium hydroxide or tetramethyl ammonium hydroxide.

The present composition is exceptionally useful as a photoresistremover, stripper or cleaner by applying the composition to eitherexposed or unexposed, i.e. cured or uncured photoresist on surfaces orsubstrates.

The composition is also an effective photoresist adhesion promoter. Thatis, when applied to a substrate and dried to a tack free state, theadhesion of a subsequently applied photoresist composition issubstantially enhanced.

The following specific examples will provide detailed illustrations ofthe present invention. These examples are not intended, however, tolimit or restrict the scope of the invention in any way and should notbe construed as providing conditions, parameters or values which must beutilized exclusively in order to practice the present invention.

EXAMPLES

A resist formulation is prepared as follows:

23.8% binder resin

7.0% photoactive compound

69.2% solvent composition comprising Cellosolve acetate, n-butyl acetateand xylene in a ratio of 8:1:1

The binder resin is a cresol-formaldehyde novolak.

The photoactive compound is the condensation product of2,1-diazonapthoquinone-5-sulfonyl chloride and1,2,3-trihydroxy-benzophenone.

The resist is coated on a silicon wafer, imagewise exposed anddeveloped. One notices a registration error in the exposing pattern andremoves the entire resist coating from the wafer by immersion in a 1:1mixture of propylene glycol methyl ether and propylene glycol methylether acetate in which is blended with 10% by weight of hexamethyldisilazane.

What is claimed is:
 1. A composition suitable for stripping, thinning,cleaning or promoting the adhesion of cured and uncured photoresistcompositions on substrates covered with such resists which consistsessentially of in admixture from about 3 to about 50% by weight of thecomposition of a hexa-alkyl disilazane and from about 50 to about 97% byweight of the composition of a solvent composition which comprises oneor more compounds selected form the group consisting of a propyleneglycol monoalkyl ether and a propylene glycol mono-alkyl ether acetate.2. The composition of claim 1 wherein said acetate is propylene glycolmethyl ether acetate.
 3. The composition of claim 1 wherein said etheris propylene glycol methyl ether.
 4. The composition of claim 1 whereinsaid hexa-alkyl disilazane is hexa-methyl disilazane.
 5. The compositionof claim 1 wherein said hexa-alkyl disilazane is present in an amount offrom about 5% to abut 30% by weight.
 6. The composition of claim 1wherein said solvent composition is present in an amount of from abut50% to about 97% by weight.
 7. The composition of claim 1 wherein saidsolvent composition is present in an amount of from about 70% to about95% by weight.
 8. The composition of claim 1 wherein both said ether andsaid acetate are present and are in a ratio of from about 1:10-10:1. 9.The composition of claim 8 wherein said ratio is from about 7:3-3:7. 10.The composition of claim 8 wherein said ratio is about 1:1.